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What is GIS? Firstly and most importantly a GIS is an information system. A system is a group of connected entities and activities which interact for a common purpose. In GIS the common purpose is decision making for managing any spatially distributed activity. Remember that: An information system is a set of processes, executed on raw data to produce information which will be useful in decision making A chain of steps leads from observation and collection of data through to analysis An information system must have a full range of tools to handle observation, measurement, description, explanation, forecasting and decision making Finally it is important to remember that GIS can also help to achieve the overall objective of improving the decision making process, whether in an organisation, or within a project.

GIS: a formal definition The most commonly quoted definition in the UK comes from the Chorley Report “Handling Geographic Information” HMSO, 1987 which is described above. Not everyone agrees with this definition. There are those who believe GIS forms part of more established disciplines but these definitions tend to ignore the cross disciplinary nature of spatial data.

Why is GIS unique? What distinguishes GIS from other information systems? GIS integrates spatial* and other kinds of information within one system: it offers a consistent framework for analysing space GIS makes connections between activities based on spatial proximity GIS provides the mechanisms for undertaking the manipulation and display of geographic knowledge *Spatial data will be described in much greater detail in the next lecture.

GIS concepts are not new! The concepts used in GIS are not new to Geographers. In the purest sense Geographers have made use of such systems for many years, but these have been manually operated - card indexes with paper map overlays, atlases and similar systems. The following is one example: In the London Cholera epidemic of 1854 Dr. John Snow was able to locate the source of the the outbreak by plotting the locations of fatal cases.

GIS: historical background GIS has developed from two independent areas: digital cartography and databases. These developments are closely related to the enormous growth in power, and the corresponding reduction in the cost of computer technology, since the late 1960’s. Digital cartography The desire to use computers to replace manual cartographic processes, particularly for the more tedious tasks, was a focus in the 1970’s. Developments in digital cartography often resulted from developments in the larger Computer Aided Design (CAD) field. At the same time the 1960’s quantitative revolution in Geography encouraged the development of computer programs that could undertake map analysis operations that would be difficult or too time-consuming to undertake by hand. Database links The use of Data Base Management Systems (DBMS) is very important to the current concept of GIS which involves the integrating of spatial and non-spatial data. The development of relational DBMS was particularly significant with examples such as Oracle being widely used today.

This is a very simple definition of what GIS is, for older students you may want to use the next slide or both together.

Geographic information system

3.
Geographical Information
System
o
•
•
•
•
•
A set of tools for
Collecting
Storing
Manipulating
Retrieving
Transforming and Display of Spatial
Data from the Real World

4.
What is a GIS?
GEOGRAPHIC
implies that locations of the data items are known, or can be
calculated, in terms of Geographic coordinates (Latitude,
Longitude)
INFORMATION
implies that the data in a GIS are organized to yield useful
knowledge, often as colored maps and images, but also as
statistical graphics, tables, and various on-screen responses to
interactive queries.
SYSTEM
implies that a GIS is made up from several inter-related and
linked components with different functions. Thus, GIS have
functional capabilities for data capture, input, manipulation,
transformation, visualization, combinations, query, analysis,
modelling and output.

5.
What is GIS?
• GIS = Geographic Information System
– Links databases and maps
– Manages information about places
– Helps answer questions such as:
•
•
•
•
•
Where is it?
What else is nearby?
Where is the highest concentration of ‘X’?
Where can I find things with characteristic ‘Y’?
Where is the closest ‘Z’ to my location?

7.
GIS: a formal definition
“A system for capturing, storing,
checking, integrating, manipulating,
analysing and displaying data which
are spatially referenced to the Earth.
This is normally considered to
involve a spatially referenced
computer database and appropriate
applications software”
7

29.
LocationAllocation
• Finding a subset of locations from a
set of potential or candidate
locations that best serve some
existing demand so as minimize
some cost
• Locate sites to best serve allocated
demand
• Application areas are warehouse
location, fast food locations, fire
stations, schools
Fundamentals of GIS

31.
Location-Allocation
Outputs
• The best sites
• The optimal allocation of
demand locations to those
sites
• Lots of statistical and
summary information about
that particular allocation
Fundamentals of GIS

33.
Synergy between spatial data
and analysis
• Imagine you are a national
retailer
• You need warehouses to
supply your outlets
• You do not wish the
warehouses to be more than
1000 km from any outlet
(Example from, ESRI)
Fundamentals of GIS

44.
Maps And Map Elements
o Maps are graphic representation of our
perception of the world around us. They
represent cartographic interpretation and
simplification of reality.
o Maps provide two types of information
o
Locational information
o
Spatial Relationships

45.
Maps contains features such
as………
Point, Line, Area and Surface
o Maps contain POINT features, LINE features and AREA
features
o Point Features :- wells, control points, sample sites, fire
stations
o Line Features :- roads, hydro lines, rivers, contour lines,
o Area Features:-urban areas, water bodies, soil/rock units,
forest areas

51.
Raster Format
• Data are divided into cell, pixels, or
elements
• Cells are organized in arrays
• Each cell has a single value
• Row and Column Numbers are used to
identify the location of the cell within the
array.
• Perhaps the most common example of
raster data is a digital image.

52.
Raster Data
A grid (or raster) system stores data as a string of
characters in which each character represents a
location.
The basic data unit is a cell or Pixel Each cell/Pixel
is assigned only one value
An array of Pixels form the entity-Point, Line,
Area and surface
The shape and size of the array determines the
basic Resolution
Polygons can be formed indicating areas of
homogeneous characteristics

53.
Vector Format
• Data are associated with points, lines, or
boundaries enclosing areas
• Points are located by coordinates
• Lines are described by a series of
connecting vectors (line segments
described by the coordinates of the start
of the vector, its direction, and magnitude
or length).
• Areas or polygons are described by a
series of vectors enclosing the area.

54.
Vector Format
• Any number of factors or attributes can be
associated with a point line or polygon.
• Data are stored in two files:
– a file containing location information
– a file containing information on the attributes
• A third file contains information needed to
link positional data with their attributes.

55.
Vector Data
 A vector system usually stores data as coordinates.
 For example Each uniform area is surrounded by a
set of straight line segments called vectors.
 In a vector based system every point is recorded by
a pair of x and Y coordinates.
 Straight line segments called vectors are displayed
to indicate line based data ( roads rivers wells)
 The x-y coordinates at the end of each vector can
be digitized and stored.
 Most spatial features can be displayed as: - PointsLine- Polygons

56.
Vector and Raster Representation
of Point Map Features
Map Feature
GIS Vector
Format
(X,Y)
Coordinate in space
GIS Raster
Format
Cell Located
in an Array

59.
Comparison of Raster and Vector
Formats
Raster
Vector
•
Raster formats are
efficient when comparing
information among arrays
with the same cell size.
•
•
Raster files are generally
very large because each
cell occupies a separate
line of data, only one
attribute can be assigned
to each cell, and cell sizes
are relatively small.
•
Vector formats are
efficient when comparing
information whose
geographical shapes and
sizes are different.
Vector files are much
smaller because a
relatively small number of
vectors can precisely
describe large areas and a
many attributes can be
ascribed to these areas.

60.
Comparison of Raster and Vector
Formats
Raster
•
Raster representations are
relatively coarse and
imprecise
Vector
•
Vector representations of
shapes can be very
precise.
Most GIS software can display both raster and
vector data. Only a limited number of programs
can analyze both types of data or make raster type
analyses in vector formats.

61.
Attribute
Attributes can be numeric or alfa-numeric
Data a point, line or area
data that is assigned to
spatial features
Example Attributes…
Stand ID, Compartment No., Vegetation
type, Name of the Forest Block, Types of
Road, VSS code etc.,

78.
SPATIAL ACCURACY
• Precision - indicates how closely several positions fall
in relation to each other
• Accuracy - is a measure of the closeness of one or
more positions to a position that is known and
defined in terms of an absolute reference system.

81.

Geospatial analysis is an approach to
applying statistical methods and other
informational techniques to data which has a
geographical or geospatial aspect. Such
analysis would typically employ software
capable of geospatial representation and
processing, and apply analytical methods to
terrestrial or geographic datasets, including
the use of GIS.

82.

Geospatial analysis, using GIS, was developed
for problems in the environmental and life
sciences, in particular ecology and geology
and It has extended to almost all industries
including defence, intelligence, utilities,
Natural Resources (i.e. Oil and Gas, Forestry
etc.), social sciences, medicine and Public
Safety (i.e. emergency management and
criminology). Spatial statistics typically
result primarily from observation rather than
experimentation.

83.



Surface analysis —in particular analysing the
properties of physical surfaces, such as gradient,
aspect and visibility, and analysing surface-like
data “fields”.
Network analysis — examining the properties of
natural and man-made networks in order to
understand the behaviour of flows within and
around such networks; and locational analysis.
Geovisualization — the creation and
manipulation of images, maps, diagrams, charts,
3D views and their associated tabular datasets.

84.
Social Factors
Biodiversity
Engineering
Land Use
Environmental
Considerations
…Means Seeing the

90.
OBJECTIVES
1-To delineate the groundwater potential zones
using relevant data (rainfall, topography, geology,
soil, etc.)
2-To develop a GIS model that can identify
groundwater potential zones based on the
thematic maps
3-To validate the results of this study with data from
the field

117.
CONCLUSIONS
1. Remote sensing images were very important
input to groundwater exploration
-the aridity and sparseness of vegetation in the
study area
-mapping of drainage from satellite imagery is
more effective than the automated derivation by
the GIS software
2. Most of the very high potential areas
represented stream channels and wadi
sediments

118.
3. Most of the promising areas are found below
800 m in elevation
4. Sensitivity analysis indicates that all
parameters are significant but the most
effective parameters : lineaments density,
geomorphology, drainage density and annual
rainfall
5. Field data were valuable in validating the GPM
output.
6. The model identified several locations suitable
for further field geophysical investigation